json_reformat

If it doesn't work for you, try yum install yajl. If you are using a mac and do not have yum, you can use macports to install json_reformat. Make sure you have xcode and macports downloaded and installed and then run sudo port install yajl. If you get an error message, follow the instructions given.

Verify a JSON

JSONView

From Firefox: Normally when encountering a JSON document (content type "application/json"), Firefox simply prompts you to download the file. With the JSONView extension, JSON documents are shown in the browser similar to how XML documents are shown. The document is formatted, highlighted, and arrays and objects can be collapsed. Even if the JSON document contains errors, JSONView will still show the raw text.